Burner for generating reductive atmosphere of exhaust gas in engine cogeneration plant having denitrification process

ABSTRACT

A burner for generating a reductive atmosphere of exhaust gas in a boiler system of an engine cogeneration plant having a denitrification process comprises a post-combustion burner for combusting an internal combustion engine exhaust gas, and an auxiliary burner installed in an outer side of the post-combustion burner. The internal combustion exhaust gas is supplied from an internal combustion engine exhaust gas injection port. The auxiliary burner is combined with a fuel injection port through which fuel is supplied, and an air channel through which air inflows. Combustion heat generated by combusting the supplied fuel and air is provided to a combustion chamber of the post-combustion burner through a flame channel.

CROSS REFERENCES

Applicant claims foreign priority under Paris Convention and 35 U.S.C.§119 to Korean Patent Application No. 10-2007-0114984, filed Nov. 12,2007 with the Korean Intellectual Property Office, where the entirecontents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a burner for generating a reductiveatmosphere of exhaust gas in an engine cogeneration plant having adenitrification process, which is to produce a catalyst activationcondition to remove nitrogen oxides from the engine exhaust gas in theengine cogeneration plant using a lean burn engine. More specifically,the present invention relates to a burner for stable combustion, inwhich one or more auxiliary burners are installed in a post-combustionburner installed in a boiler of an engine cogeneration plant.

2. Background of the Related Art

In general, an internal combustion engine is described by a motive powerwhere fuel is supplied into a cylinder and then the fuel is burned andexploded to generate a gas, of which expansion force is utilized to movea piston. A boiler is described by an apparatus that produceshigh-pressure steam or hot water by heating water, and is mainly used ina heating facility, a bathhouse, and as an industrial heat source forturbine driving, and the like.

FIG. 1 is a block diagram showing a conventional engine cogenerationplant capable of reducing nitrogen oxides. The engine cogeneration planeof FIG. 1 is disclosed in U.S. Pat. No. 5,022,226 and includes aninternal combustion engine 1, a generator 2, a post-burner 3, a boiler4, catalyst beds 5 and 6, a fuel saving unit 7 and a chimney.

In the above cogeneration plant, fuel and oxygen are supplied to aninternal combustion engine 1 to generate electricity, and the heat ofexhaustion gas is used to produce steam. Here, the combustion exhaustgas stream is recovered from the internal combustion engine 1 at about500 to 1000° F. and contains about 6 to 15% of oxygen. The stream havingsufficient fuel is supplied a thermal reaction means required to reactthe fuel, nitrogen oxides and available oxygen, thereby generating areduced oxygen stream. The reduced oxygen stream is cooled inside a heatexchanger. Depending on reduction condition, conversion oxygen issupplied to the cooled stream before being supplied to the catalyst bed.The oxygen may be provided directly with air. More preferably, theoxygen may be supplied after being discharged from the internalcombustion engine 1 and passing through the exhaust stream channel. Theconversion oxygen stoichiometrically exceeds the amount of nitrogenoxygen, but is less than the amount of combustible materials. Accordingto the result, the nitrogen oxides inside the stream are treated intonitrogen dioxide at the final end portion before the catalyst bed.Thereafter, the nitrogen dioxide is reduced at the remaining portion ofthe catalyst bed 6 due to excessive combustible materials. The stream,where the amount of nitrogen oxide is considerably reduced, isdischarged.

The exhaust gas discharged from the internal combustion engine 1 istransferred to a thermal reactor such as the post-burner 3 and burned at1800 to 3200° F., preferably 2000 to 2400° F. Gaseous harmful substanceshave 1800 to 3200° and contains about 750 ppmv of nitrogen oxides. Theabove stream passes through a heat exchanger. The harmful substance iscooled to about 600 to 1050° F., preferable 750 to 900° F. The valuescorresponding to the exhaust stream are obtained at the boiler 4, andsteam is produced accordingly. The exhaust gas discharged from theboiler, which contains sufficient fuel and cooled, is mixed with adesired amount of conversion oxygen before passing through the catalystbed 5 and added to the duct 9 at 14. As described above, the oxygen isadded directly to the air supplier 14, but may be added through adesired channel of the engine exhaust unit from the duct 11 via a line13. Due to this construction, the amount of oxygen injected to thepost-burner 3 can be reduced. Therefore, the amount of fuel required tothe post-burner can be reduced. The important purpose of conversionoxygen is accomplished, depending on the mixture injected into thecatalyst bed 5.

In particular, the amount of conversion oxygen added to the cooled steamfrom the boiler 4 exceeds that of nitrogen oxides within the stream, butis less than the combustible substances within the stream. In general,the added oxygen is about 20.2 to 0.9%. The nitrogen oxides in the line9 are in the form of nitrogen monoxide. The mixture is injected throughthe front end portion of the catalyst bed 5, where the oxygen is reactedwith nitrogen monoxide to be converted in the form of nitrogen dioxide.

The amount of oxygen within the duct 16, which is placed under thecatalyst bed 6, is 1.5 to 3%. The value of the nitrogen oxides withinthe duct 16 is 15 ppmv and the carbon monoxide is reduced to below 50ppmv. The oxidized gaseous harmful substances discharged from thecatalyst bed 6 are transferred to the fuel saving unit 7 or the lowpressure waste heat boiler from the duct 16. The cooled gas having about300 to 400° F. is input to the chimney 8 via the discharge duct 17 anddischarged to the atmosphere. The nitrogen oxides being discharged arebelow 15 ppmv and the carbon monoxide is below 50 ppmv.

FIG. 2 shows a low oxygen turbulence burner disclosed in Korean PatentPublication No. 10-0667223. FIG. 3 is a cross-sectional view taken alongthe line A-A′ in FIG. 2. Referring to FIG. 2, exhaust gas generated inthe internal combustion engine of a boiler is used as a combustion airsupply source to be re-combusted. Thus, the exhaust gas is discharged inthe completely combusted state and is prevented from contaminating thenatural environment. The exhaust gas inflows into an injection space andis primarily mixed with fuel sprayed through a nozzle 31 whilegenerating turbulence by means of an outer case 25, and then sprayedthrough the nozzle 31 while passing through an orifice 30. Referring toFIG. 3, a turbulence pipe 32 is installed to be inclined at 20 to 60degrees in parallel with the tangential direction of the outer case 25.When the exhaust gas inflows into inside of the outer case 25, it isconverted into an eddy current by means of contacting with the innerside of the outer case 25 and discharged towards an outlet port offunnel shape.

According to a technique disclosed in Korean Patent Publication No.10-0667223, fuel is supplied to a combustion chamber 21 while beingmixed again and combusted therein. Flame generated in the combustionchamber 21 is re-circulated inside the combustion chamber 21 andincompletely combusted fuel is burned by a choke 23, thereby savingenergy and improving heat efficiency of the boiler.

In addition, as the prior art related to the present invention, KoreanPatent Publication No. 10-0253991 discloses a method of reducingnitrogen oxides in a boiler, which is a low pollution type burner.According to this technique, the fuel nozzle of a low nitrogen oxideburner, which is disposed in the upper end row of the burner unit, isreplaced to increase the amount of fuel being sprayed, or the size ofthe nitrogen oxide burner is reduced to decrease the amount ofcombustion air being sprayed.

However, in the conventional techniques, the exhaust gas from aninternal combustion engine is mixed with oxygen and supplied to aburner. Thus, the concentration of oxygen is low so that the combustionis unstable and thus flame cannot be properly formed. Accordingly, inorder to meet a stable combustion condition, the concentration of oxygenis required to increase and a larger amount of fuel is to be consumed asmuch as the amount of air being additionally supplied.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made in view of theabove-mentioned problems occurring in the prior art, and it is a primaryobject of the present invention to provide a burner for generating areductive atmosphere of exhaust gas in an engine cogeneration planthaving a denitrification process, in which in order to produce acatalyst activation condition to remove nitrogen oxides from the engineexhaust gas in the boiler of the engine cogeneration plant, a mixture ofthe engine exhaust gas and fuel is injected into an engine exhaust gasinjection port and a stable combustion can be maintained by means of anauxiliary burner.

To accomplish the above object of the present invention, according tothe present invention, there is provided a burner for generating areductive atmosphere of exhaust gas in a boiler system of an enginecogeneration plant having a denitrification process. The burnercomprises: a post-combustion burner for combusting an internalcombustion engine exhaust gas, the internal combustion exhaust gas beingsupplied from an internal combustion engine exhaust gas injection port;and an auxiliary burner installed in an outer side of thepost-combustion burner, wherein the auxiliary burner is combined with afuel injection port through which fuel is supplied, and an air channelthrough which air inflows; and combustion heat generated by combustingthe supplied fuel and air is provided to a combustion chamber of thepost-combustion burner through a flame channel.

A combustible mixture gas is injected to the post-combustion burnerthrough the internal combustion engine exhaust gas injection port. Thecombustible mixture gas contains fuel more than to the extent to removeoxygen contained in the internal combustion engine exhaust gas. Inaddition, new air through a blower and fuel are injected at the sametime to the auxiliary burner and combusted therein.

The new air is injected to an air injection port and recovers heattransferred from a combustion flame inside the combustion chamber whilepassing through the air channel, thereby enabling to prevent heat lossand safety accidents.

The burner further comprises a damper capable of adjusting the amount ofa combustible mixture gas to be supplied to the front and rear sides ofthe flame of the auxiliary burner after being injected to the internalcombustion engine exhaust gas injection port, thereby enabling to adjustcombustion conditions. The combustible mixture gas is a mixture ofinternal combustion engine exhaust gas and fuel.

The present invention generates a stable reductive atmosphere requiredfor denitrification catalyst to remove nitrogen oxides, which isproduced in engine exhaust gas of an engine cogeneration plant using alean burn engine. According to the present invention, fuel is injectedinto the engine exhaust gas in advance, and thus a combustible mixturegas of the engine exhaust gas and fuel is injected through an injectionport. A new air and fuel are supplied to an auxiliary burnerrespectively and combusted therein, thereby enabling to achieve, in astable way, a reductive atmosphere having oxygen of no more than 1% andcarbon monoxide of about 1000 ppmv.

At this time, the total amount of fuel being supplied is made to be anamount necessarily required to consume 6 to 12% of oxygen contained inthe exhaust gas of the internal combustion engine and for thepost-combustion burner to be operated in a stale way.

In particular, fuel is divided and supplied to the internal combustionengine exhaust gas injection port and the auxiliary burner and theauxiliary burner carries out combustion using the new air. Thus, sincethe internal combustion engine exhaust gas and fuel are supplied in amixed state, a stable flame can be formed, notwithstanding that thecombustible mixture gas contains a low oxygen content of 6 to 12%. Inaddition, the amounts of the auxiliary fuel and the new air can bevaried to maintain an optimum combustion condition, thereby enabling tomaximize efficiency of the cogeneration plant.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofthe preferred embodiments of the invention in conjunction with theaccompanying drawings, in which:

FIG. 1 is a block diagram showing a conventional engine cogenerationplant capable of reducing nitrogen oxides;

FIG. 2 shows a conventional turbulence burner;

FIG. 3 is a cross-sectional view taken along the line A-A′ in FIG. 2;

FIG. 4 is an exploded perspective view of a post-combustion burneraccording to an embodiment of the invention;

FIG. 5 is a front sectional view of the post-combustion burner of FIG.4;

FIG. 6 is a side sectional view of the post-combustion burner of FIG. 4;and

FIG. 7 is a cross-sectional view taken along the line B-B′ in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereafter, exemplary embodiment of the present invention will bedescribed in detail with reference to the appended drawings.

FIG. 4 is an exploded perspective view of a post-combustion burneraccording to an embodiment of the invention. FIG. 5 is a front sectionalview of the post-combustion burner of FIG. 4. FIG. 6 is a side sectionalview of the post-combustion burner of FIG. 4. This embodimentillustrates an improvement in the structure of the boiler of FIG. 1.

As illustrated in FIGS. 4 and 5, in the structure of a post-combustionburner, which is equipped in a boiler, a mixture of engine exhaust gasand fuel is injected through an injection port 40 of internal combustionengine exhaust gas. The injection port 40 is combined to an outer case45 by means of a first flange 42. Installed at both sides of thepost-combustion burner are two auxiliary burners 51 and 54. The firstauxiliary burner 51 is combined with a fuel injection port 52 and an airchannel 53 and combined with the outer case 45 of the post-burner bymeans of a second flange 46. The first auxiliary burner 51 is connectedinto a combustion chamber 57 of the post-combustion burner through aflame channel 58.

The second auxiliary burner 54 is also combined with the fuel injectionport 55 and the air channel 56 and combined with the outer case of thepost-combustion burner by means of a third flange 47. The secondauxiliary burner 54 is connected into the combustion chamber 57 of thepost-combustion burner through the flame channel 59. Reference numeral44 denotes a viewing window, 60 denotes a ceramic refractory, 61 denotesan injection port for new air flowing from a blower, and 62 denotes achannel for the new air being supplied to the auxiliary burners.

It is preferable that the above auxiliary burners 51 and 54 areinstalled at the lower half portion of the post-combustion burner at acertain angle. In addition, when required, it is preferable that one ormore than two auxiliary burners are installed in the post-combustionburner.

FIG. 6 is a side sectional view of the post-combustion burner, and FIG.7 is a cross-sectional view taken along the line B-B′. As illustrated inFIGS. 6 and 7, in the present invention, when the combustible mixturegas of the internal combustion engine exhaust gas and fuel is injectedthrough the exhaust gas injection port 40, the combustible mixture gasis divided to the left and right sides by means of a damper 43 and thensupplied to the front and rear side of the combustion chamber 57, whereflame produced in the auxiliary burners 51 and 54 is provided. Here, thedivision ratio by the damper 43 can be adjusted in order to optimizecombustion conditions.

Further, if a new air being supplied from the blower is supplied to theair injection port 61, the new air passes through an air channel 62 atthe outermost of the post-combustion burner and again supplied to thetwo auxiliary burners 51 and 54 by means of a new air supply channels 53and 56. The combustion heat from the auxiliary burner is supplied to thecombustion chamber 57 of the post-combustion burner through the flamechannel 59.

Accordingly, the combustion chamber of the post-combustion burner issupplied with a high-temperature combustion heat and heats thecombustible mixture gas of the internal combustion engine exhaust gasand fuel to achieve, in a stable manner, a reductive atmosphere havingoxygen no more than 1% and carbon monoxide of about 1000 ppmv.

Furthermore, the operator can view through the viewing window thecombustion condition of flame inside the combustion chamber 57.

Conventionally, the internal combustion engine exhaust gas and newlysupplied air are mixed in advance and then injected into the internalcombustion engine exhaust gas injection port 40. Therefore, since theconcentration of oxygen becomes lower, the combustion can not occur in astable manner.

However, in this embodiment of the invention, the combustible mixturegas of the internal combustion engine exhaust gas and fuel is injectedinto the internal combustion engine exhaust gas injection port 40. Here,the amount of fuel being supplied is to the extent that the 6 to 12%oxygen contained in the internal combustion engine exhaust gas can beconsumed.

In the embodiments of the invention, the auxiliary burner is installedin order to combust in a stable manner the combustible gas, which isinjected through the internal combustion engine exhaust gas injectionport. The flame generated in the auxiliary burner is supplied to insideof the combustion chamber 57 of the post-combustion burner and producesturbulence. Thus, the staying time of the flame becomes longer such thatthe combustible gas inside the combustion chamber can be completelycombusted. The basic principles are generally known and the turbulenceburner in FIG. 2 or the like is utilized. In addition, the presentinvention can be applied to a water tube packaged boiler, as well as asmoke tube packaged boiler.

In the embodiments of the present invention, new air, which is suppliedto the auxiliary burners 51 and 54 from the blower, is injected to thenew air injection port 61. While the new air passes through theoutermost air channel 62 of the post-combustion burner, the heat beingtransferred from a channel of 450° C. or combustion flame of above 1200°C. is shield by the new air and absorbed to the air, and then used againin the combustion chamber, thereby enabling to reduce heat loss andsimultaneously secure safety for fire or skin burn, which may be causedby an increase on the surface temperature of the post-combustion burner.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by theembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

1. A burner for generating a reductive atmosphere of exhaust gas in aboiler system of an engine cogeneration plant having a denitrificationprocess, the burner comprising: a post-combustion burner for combustingan internal combustion engine exhaust gas, the internal combustionexhaust gas being supplied from an internal combustion engine exhaustgas injection port; and an auxiliary burner installed in an outer sideof the post-combustion burner, wherein the auxiliary burner is combinedwith a fuel injection port through which fuel is supplied, and an airchannel through which air inflows; and combustion heat generated bycombusting the supplied fuel and air is provided to a combustion chamberof the post-combustion burner through a flame channel.
 2. The burneraccording to claim 1, wherein a combustible mixture gas is injected tothe post-combustion burner, the combustible mixture gas containing fuelto the extent to remove oxygen contained in the internal combustionengine exhaust gas.
 3. The burner according to claim 1, wherein the airbeing supplied to the auxiliary burner is injected to an air injectionport and recovers heat transferred from a combustion flame inside thecombustion chamber while passing through the air channel.
 4. The burneraccording to claim 1, further comprising a damper capable of adjustingthe amount of a combustible mixture gas to be supplied to the combustionchamber of the post-combustion burner after being injected to theinternal combustion engine exhaust gas injection port, the combustiblemixture gas being a mixture of internal combustion engine exhaust gasand fuel.
 5. The burner according to claim 1, wherein a combustionchannel of the auxiliary burner is installed in a tangential directionof the combustion chamber to cause turbulent flame so that the flameremains inside the combustion chamber for a longer period of time. 6.The burner according to claim 1, wherein the auxiliary burner includestwo or more auxiliary burners.